Swarm of flies react to singing. Why??

A few years ago I discovered an interesting insect behaviour whereby I could seemingly control large swarms of tiny flies/gnats simply by singing a range of tones to them. I first noticed this in the UK in 2004 but have since been able to replicate the experiment several times here in Australia and more recently captured it on video near the town of Woolgoolga in NSW. Initially I noticed that a swarm of gnats above me seemed to slow their frantic movement when I started to speak and after a little experimentation I discovered that certain higher pitched vocals would cause the flies to noticeably rise upwards as a group and then rapidly drop downwards again upon ceasing the tone. I’ve noticed this both with gnats in a forest environment and also with sand fly swarms at the beach. What’s also interesting is the flies seem to have excellent hearing over quite some distance as I have seen them reacting to a dog barking perhaps 50m away. I’d be interested to know if anyone has ever